Recently sinced i moved, my PC has been giveing me a lot of problems (understatement).
1)It always freezes up, it does this when i am extracting a large game for example halo or halflife2,

whenever i am running a virus scan in stall, wheneer i am defragmenting it stalls.

I treid resolving this by changing antivirus and using a diferent on i worked and i managed to do a deep system virus scan, but i found no viruses.
2) My computer tends to shutdown by it self, for example i am doing by practicals on MWord and i alt + tab to the new screen, it simply crashes and resttarts. I comes to the desktop saying windows recovered from a serious error.
What can i do to stop this
ANy helpwould be reatly appreaciated